High-pressure tank mounting structure

ABSTRACT

A high-pressure tank mounting structure includes: a case disposed beneath a floor of a vehicle cabin and having a bottom wall, a peripheral wall and a top wall; and a plurality of high-pressure tanks accommodated so as to be lined up within the case, wherein a first hydrogen collection portion that is recessed upwardly is formed at a back surface of the top wall of the case, and a hydrogen sensing sensor is disposed at the first hydrogen collection portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese PatentApplication No. 2017-154168 filed Aug. 9, 2017, the disclosure of whichis incorporated by reference herein in its entirety.

BACKGROUND Technical Field

Preferred embodiments relate to a high-pressure tank mounting structure.

Related Art

A high-pressure tank mounting structure is disclosed in Japanese PatentApplication Laid-Open (JP-A) No. 2009-270707. In this mountingstructure, high-pressure tanks (hydrogen tanks) are accommodated withina case for hydrogen storing bodies that forms a closed space.

SUMMARY

However, in the aforementioned related art, there is the problem thathydrogen that has permeated from the high-pressure tanks stagnateswithin the case.

In consideration of the above-described circumstances, an object ofpreferred embodiments is to provide a high-pressure tank mountingstructure that accommodates high-pressure tanks in a case, and that caneasily sense hydrogen that has permeated from the high-pressure tanks.

A high-pressure tank mounting structure of a first aspect of the presentdisclosure includes: a case that is disposed beneath a floor of avehicle cabin, and that has a bottom wall, a peripheral wall and a topwall; and plural high-pressure tanks that are accommodated so as to belined up within the case, wherein a first hydrogen collection portionthat is recessed upwardly is formed in a back surface of the top wall ofthe case, and a hydrogen sensing sensor is disposed at the firsthydrogen collection portion.

In the high-pressure tank mounting structure of the first aspect, thecase, which has the bottom wall, the peripheral wall and the top wall,is disposed beneath the floor of a vehicle cabin. The pluralhigh-pressure tanks are accommodated so as to be lined up in the case.Due thereto, in a high-pressure tank mounting structure in which pluralhigh-pressure tanks are disposed beneath the floor of a vehicle cabin,the high-pressure tanks can be protected from interference with the roadsurface and from fire.

Moreover, in this high-pressure tank mounting structure, the firsthydrogen collection portion that is recessed upwardly is formed at theback surface of the top wall of the case, and the hydrogen sensingsensor is disposed at this first hydrogen collection portion. Duethereto, hydrogen, which has permeated form the high-pressure tanks, canbe accumulated in the first hydrogen collection portion, and thisaccumulated hydrogen can be sensed by the hydrogen sensing sensor.Accordingly, the hydrogen can be sensed easily.

The high-pressure tank mounting structure of a second aspect of thepresent disclosure, in the high-pressure tank mounting structure of thefirst aspect, further includes a discharging mechanism that discharges,to an exterior of the case, hydrogen that has been accumulated at thefirst hydrogen collection portion.

In the high-pressure tank mounting structure of the second aspect, thedischarging mechanism, which discharges the hydrogen that has beenaccumulated at the first hydrogen collection portion, is provided. Duethereto, the hydrogen can be discharged effectively.

In a high-pressure tank mounting structure of a third aspect of thepresent disclosure, in the high-pressure tank mounting structure of thesecond aspect, the discharging mechanism includes: a discharge hole thatcommunicates an interior of the case with the exterior of the case; ashutter that opens and closes the discharge hole; and a control sectionthat controls opening and closing of the shutter in accordance withoutput of the hydrogen sensing sensor.

In the high-pressure tank mounting structure of the third aspect, thedischarging mechanism is structured to include the discharge hole, theshutter and the control section. The interior and the exterior of thecase are communicated by the discharge hole, and the discharge hole isopened and closed by the shutter. Further, the control section controlsthe opening and closing of the shutter in accordance with the output ofthe hydrogen sensing senor. Due thereto, by opening the shutter only incases in which hydrogen is sensed for example, the hydrogen isdischarged appropriately while penetration of water and the like fromthe exterior can be suppressed.

In a high-pressure tank mounting structure of a fourth aspect of thepresent disclosure, in the high-pressure tank mounting structure of anyof the first through third aspects, the first hydrogen collectionportion is positioned at a vehicle longitudinal direction centralportion and a vehicle transverse direction central portion of the topwall.

In the high-pressure tank mounting structure of the fourth aspect, thefirst hydrogen collection portion is positioned at the vehiclelongitudinal direction central portion and the vehicle transversedirection central portion of the top wall. Due thereto, the hydrogen canbe accumulated efficiently in the first hydrogen collection portion, ascompared with a structure in which the first hydrogen collection portionis positioned only in a vicinity of an edge portion of the top wall asseen in a vehicle plan view.

In a high-pressure tank mounting structure of a fifth aspect of thepresent disclosure, in the high-pressure tank mounting structure of anyof the first through fourth aspects, a guide portion, which is inclineddownwardly toward an outer edge portion of the top wall, is formed in atleast one of a front side, a rear side, a right side and a left side ofthe first hydrogen collection portion.

In the high-pressure tank mounting structure of the fifth aspect, theguide portion, which is inclined downwardly toward an outer edge portionof the top wall, is formed in at least one of the front side, the rearside, the right side and the left side of the first hydrogen collectionportion. Due thereto, the hydrogen that is at the outer edge portion ofthe top wall can be guided by the guide portion to the first hydrogencollection portion.

In a high-pressure tank mounting structure of a sixth aspect of thepresent disclosure, in the high-pressure tank mounting structure of anyof the first through fourth aspects, guide portions, which are inclineddownwardly toward outer edge portions of the top wall, are formed at allof a front side, a rear side, a right side and a left side of the firsthydrogen collection portion.

In the high-pressure tank mounting structure of the sixth aspect, theguide portions, which are inclined downwardly toward outer edge portionsof the top wall, are formed at all of the front side, the rear side, theright side and the left side of the first hydrogen collection portion.Due thereto, the hydrogen can be guided to the first hydrogen collectionportion from the outer edge portions of the top wall by the guideportions of the four directions.

In a high-pressure tank mounting structure of a seventh aspect of thepresent disclosure, in the high-pressure tank mounting structure of anyof the first through fourth aspects, the first hydrogen collectionportion is positioned at a vehicle transverse direction central portionof the top wall, a guide portion, which is inclined downwardly toward anouter edge portion of the top wall, is formed at a front side or a rearside of the first hydrogen collection portion, and, as seen in a vehicleplan view, the first hydrogen collection portion and the guide portionare configured to overlap a tunnel portion of a floor panel thatstructures a floor portion of the vehicle cabin.

In the high-pressure tank mounting structure of the seventh aspect, thefirst hydrogen collection portion is positioned at the vehicletransverse direction central portion of the top wall. The guide portion,which is inclined downwardly toward an outer edge portion of the topwall, is formed at the front side or the rear side of the first hydrogencollection portion. Further, as seen in a vehicle plan view, the firsthydrogen collection portion and the guide portion overlap the tunnelportion of the floor panel that structures the floor portion of thevehicle cabin. Due thereto, by utilizing, of the floor panel, the tunnelportion that is convex upwardly, it is possible to place a portion ofthe case at a relatively upper side of the vehicle.

In a high-pressure tank mounting structure of an eighth aspect of thepresent disclosure, in the high-pressure tank mounting structure of anyof the fifth through seventh aspects, a second hydrogen collectionportion, which is recessed upwardly and is positioned further toward avehicle lower side than the first hydrogen collection portion, is formedat a back surface of an outer peripheral portion of the top wall.

In the high-pressure tank mounting structure of the eighth aspect, thesecond hydrogen collection portion, which is recessed upwardly and ispositioned further toward the vehicle lower side than the first hydrogencollection portion, is formed at the back surface of the outerperipheral portion of the top wall. Due thereto, the hydrogen can beguided from the second hydrogen collection portion via the guideportion(s) to the first hydrogen collection portion. Because the outerperipheral portion of the top wall is a portion where hydrogen is apt toaccumulate due to tilting of the vehicle, discharging of the hydrogencan be carried out effectively.

As described above, the high-pressure tank mounting structures of therespective aspects of the present disclosure have the excellent effectof, in a high-pressure tank mounting structure in which high-pressuretanks are accommodated in a case, being able to easily sense hydrogenthat has permeated from the high-pressure tanks.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments will be described in detail based on the followingfigures, wherein:

FIG. 1 is a schematic side view showing a fuel cell vehicle in which ahigh-pressure tank unit is mounted;

FIG. 2 is an exploded perspective view of a high-pressure tank unit ofan embodiment;

FIG. 3 is a schematic drawing showing a hydrogen sensing sensor and adischarging mechanism that are provided at a first hydrogen collectionportion;

FIG. 4 is a cross-sectional view showing a state in which thehigh-pressure tank unit of the embodiment is cut at a vehicle transversedirection central portion along a plane that is orthogonal to thevehicle transverse direction;

FIG. 5 is a cross-sectional view showing a state in which thehigh-pressure tank unit of the embodiment is cut along a plane that isorthogonal to the vehicle longitudinal direction;

FIG. 6 is a drawing schematically showing movement of hydrogen which haspermeated in the embodiment;

FIG. 7 is a cross-sectional view showing a state in which ahigh-pressure tank mounting structure of modified example 1 is cut alonga plane that is orthogonal to the vehicle longitudinal direction;

FIG. 8 is a drawing schematically showing movement of hydrogen which haspermeated in modified example 1;

FIG. 9 is a cross-sectional view showing a state in which ahigh-pressure tank mounting structure of modified example 2 is cut alonga plane that is orthogonal to the vehicle transverse direction;

FIG. 10 is a drawing schematically showing movement of hydrogen whichhas permeated in modified example 2;

FIG. 11 is a drawing schematically showing movement of hydrogen whichhas permeated in modified example 3; and

FIG. 12 is a drawing schematically showing movement of hydrogen whichhas permeated in modified example 4.

DETAILED DESCRIPTION First Embodiment

A high-pressure tank mounting structure Si relating to a firstembodiment of the present invention is described hereinafter.

Note that arrow FR that is shown appropriately in the respectivedrawings indicates the vehicle forward side, arrow UP indicates thevehicle upward side, and arrow LH indicates the vehicle transversedirection left side. Further, when longitudinal, vertical and left-rightdirections are used in the following description without beingspecified, they refer to the longitudinal of the vehicle longitudinaldirection, the vertical of the vehicle vertical direction and the leftand right of the vehicle transverse direction.

As shown in FIG. 1, a fuel cell vehicle 11 (hereinafter called “vehicle11”) to which the high-pressure tank mounting structure Si is applied isstructured to include a driving motor 12, an FC stack 14 (fuel cellstack), and a high-pressure tank unit 10.

In the present embodiment, as an example, the driving motor 12 isdisposed at a vehicle rear portion. Due to the driving motor 12 driving,output from the driving motor 12 is transmitted via an unillustratedtransmission mechanism to rear wheels 13.

Further, the FC stack 14 is disposed at a vehicle front portion. The FCstack 14 is a stacked structure in which plural single cells, which arestructural units, are stacked together, and the FC stack 14 functions asa high-voltage power source. Further, each single cell that structuresthe FC stack 14 generates electric power by an electrochemical reactionof hydrogen gas, which is supplied from the high-pressure tank unit 10that is described later, and compressed air that is supplied from anunillustrated air compressor. Further, an unillustrated storage batteryis provided at the vehicle 11. The storage battery is achargeable/dischargeable battery, and a nickel-hydrogen secondarybattery, a lithium-hydrogen secondary battery, or the like is usedtherefor. Due to electric power being supplied from this storage batteryto the driving motor 12, the driving motor 12 is driven, and regeneratedelectric power is recovered from the driving motor 12 at times ofdeceleration regeneration.

The high-pressure tank unit 10 is disposed at a vehicle lower side of afloor panel 16 that structures a floor portion of the vehicle cabin. Asshown in FIG. 2, the high-pressure tank unit 10 is structured to includea case 22, plural high-pressure tanks 18, and manifolds 20, 21.

The high-pressure tanks 18 are formed in substantially cylindricalshapes that are elongated and whose axial directions are the lengthdirections. The plural high-pressure tanks 18 are arrayed adjacent toone another. In the present embodiment, as an example, eleven of thehigh-pressure tanks 18 are disposed at a uniform interval in the vehicletransverse direction, with the axial directions thereof being along thevehicle longitudinal direction.

Further, positions of vehicle front side end portions of the elevenhigh-pressure tanks 18 are aligned. Seven high-pressure tanks 18 thatare at a vehicle central region are formed to have the same lengths inthe axial direction. On the other hand, vehicle longitudinal direction(axial direction) lengths of two high-pressure tanks 18 at a vehicleleft side and two high-pressure tanks 18 at a vehicle right side areformed to be shorter than those of the other high-pressure tanks 18.Therefore, the rear end portions of these four high-pressure tanks 18are positioned further toward a vehicle front side than the rear endportions of the other high-pressure tanks 18.

Each of the high-pressure tanks 18 is structured to include a bodyportion 24 and mouthpieces 30. The body portion 24 is formed in theshape of a cylinder whose axial direction both end portions are open. Inthe present embodiment, as an example, the body portion 24 is formed ofan aluminum alloy.

The mouthpieces 30 are provided at the axial direction both end portionsof the body portion 24. The both end portions of the body portion 24 areclosed-off by the mouthpieces 30. The mouthpiece 30 at a vehicle frontend side and the mouthpiece 30 at a vehicle rear end side are structuredsimilarly. The mouthpieces 30 have connecting portions 30A, and themanifolds 20, 21 are connected to the connecting portions 30A.

The high-pressure tanks 18 are connected in the vehicle transversedirection by the manifolds 20, 21. The manifold 20 (the valve-sidemanifold) is disposed at a vehicle front side of the high-pressure tanks18, and is an elongated tubular body that extends in the vehicletransverse direction (the direction in which the high-pressure tanks 18are arrayed). Connecting portions 20A that are connected to theconnecting portions 30A of the mouthpieces 30 are provided at themanifold 20. The plural connecting portions 20A are provided so as tocorrespond to the respective positions of the high-pressure tanks 18,and, in the present embodiment, eleven of the connecting portions 20Aare provided. A flow path is formed at an interior of the manifold 20.Interiors of the plural high-pressure tanks 18 communicate with oneanother by this flow path. Plural front side mounting pieces 36 areprovided at the manifold 20. The plural (three in the presentembodiment) front side mounting pieces 36 are lined up in the vehicletransverse direction, and are fixed to a bottom wall 44 of the case 22by plural brackets 60.

A lead-out pipe 32 is provided at a vehicle transverse directionintermediate portion of the manifold 20 (the intermediate portion in thedirection in which the high-pressure tanks 18 are arrayed). The lead-outpipe 32 is a tubular body that projects-out toward a vehicle front sidefrom the manifold 20. The lead-out pipe 32 is provided at the sameposition in the vehicle transverse direction as the connecting portion20A that is at a vehicle transverse direction center at the manifold 20.

On the other hand, the manifold 21 is disposed at a vehicle rear side ofthe high-pressure tanks 18. Rear end portions of the high-pressure tanks18 are connected in the vehicle transverse direction by the manifold 21.The manifold 21 has plural (in the present embodiment, eleven)connecting portions 21A, in the same way as the manifold 20. Theseconnecting portions 21A have insert-through holes through which theconnecting portions 30A of the mouthpieces 30 are inserted. A flow pathis formed at an interior of the manifold 21, and the interiors of theplural high-pressure tanks 18 communicate with one another by this flowpath. Moreover, plural rear side mounting pieces 38 are provided at themanifold 21. The plural (three in the present embodiment) rear sidemounting pieces 38 are lined up in the vehicle transverse direction, andare fixed to the bottom wall 44 of the case 22 by plural brackets 62.

The high-pressure tanks 18 and the manifolds 20, 21 are accommodated inthe case 22. The case 22 is formed in the shape of a box that issubstantially rectangular as seen in plan view. The case 22 isstructured to include a case main body 40 and a cover member 42.

The case main body 40 is a box whose upper side is open, and isstructured by the bottom wall 44 and a peripheral wall 46. The bottomwall 44 is made of an aluminum alloy or the like, and, as seen in planview, is a substantially rectangular shape whose corners are rounded.Further, plural mounting holes 44A are formed with intervalstherebetween in an outer peripheral portion of the bottom wall 44.Fastening members such as bolts or the like are passed-through themounting holes 44A, and the bottom wall 44 of the case 22 is fastened tovehicle body frame members such as rockers or the like.

The peripheral wall 46 stands erect on the bottom wall 44. Theperipheral wall 46 is formed by an extrusion molded product of analuminum alloy, and is rectangular frame-shaped as seen in plan view.

The peripheral wall 46 is structured to include a front wall 48 thatextends in the vehicle transverse direction at to vehicle front side, arear wall 50 that extends in the vehicle transverse direction at avehicle rear side, and a right wall 52 and a left wall 53 that connectthe both end portions of the front wall 48 and the rear wall 50 in thevehicle longitudinal direction. Further, the front wall 48, the rearwall 50, the right wall 52 and the left wall 53 are respectively closedcross-sectional structures. Concretely, cross-sectional structures ofthe front wall 48, the rear wall 50, the right wall 52 and the left wall53 are respectively closed-off structures that are shaped as rectangleswhose lengths run along the vertical direction, and further haveintermediate walls that divide these rectangles into upper and lowerportions.

Further, a through-hole 48A that passes-through the front wall 48 in thevehicle longitudinal direction is formed in a vehicle transversedirection central portion of the front wall 48. The lead-out pipe 32that is provided at the manifold 20 is led-out through the through-hole48A to the exterior of the case 22. A valve 34 that can open and closethe flow path of the manifold 20 is provided at the lead-out pipe 32.The amount of fluid flowing within the flow path can be controlledthereby. One end portion of an unillustrated pipe is connected to thevalve 34, and the other end portion of this pipe is connected to thefuel cell stack or the like.

Vehicle transverse direction both sides of the rear end portion of theperipheral wall 46 are concave portions 51 that are recessed toward thevehicle front side as seen in plan view. (Only the concave portion 51 atthe vehicle left side is illustrated in FIG. 2.) Therefore, a length ofthe interior of the case 22 along the vehicle longitudinal direction isshorter at the vehicle transverse direction both end portions than at avehicle transverse direction central portion. Thus, the high-pressuretanks 18 that are accommodated at the vehicle transverse direction bothsides are containers whose lengths in the vehicle longitudinal direction(the axial directions thereof) are shorter than those of the otherhigh-pressure tanks 18.

The opening at the upper side of the case main body 40 is closed-off bythe cover member 42. The cover member 42 is formed in the shape of aflat plate of an aluminum alloy or the like, and is a shape thatcorresponds to the peripheral wall 46. Therefore, cut-out portions 42A,which are cut-out toward the vehicle front side as seen in a plan view,are formed in vehicle transverse direction both end portions of a rearend portion of the cover member 42 in correspondence with the concaveportions 51 of the peripheral wall 46. A step 42B is formed at an outerperipheral end portion of the cover member 42. The portion, which isfurther toward the outer side than this step 42B, is superposed on a topsurface of the peripheral wall 46, and is fastened thereto by fasteningmembers such as bolts or the like.

As shown in FIG. 2, a convex portion 71, which is convex upwardly withrespect to general portions 72 of a top wall 70, is formed at the topwall 70. The top wall 70 is further toward the inner side than the step42B at the cover member 42. The convex portion 71 is formed by pressworking for example. The general portions 72 extend in the vehiclehorizontal direction.

Due to the convex portion 71 being formed, a back surface of the topwall 70 is, at the convex portion 71, a concave portion that is recessedupward. The convex portion 71 is formed in the shape of a cross as seenin a vehicle plan view. A central portion of this cross-shaped convexportion 71 is the most upwardly convex. Namely, at the central portionof the cross-shaped convex portion 71, the back surface of the top wall70 is recessed the most upward, and the central portion of thecross-shaped convex portion 71 is the highest point in the verticaldirection of the back surface of the top wall 70. Due thereto, thehydrogen, which has permeated from the high-pressure tanks 18 and whosespecific gravity is low, is accumulates at the central portion of thecross-shaped convex portion 71. Namely, the central portion of thecross-shaped convex portion 71 functions as the “first hydrogencollection portion 73” where the hydrogen is accumulated.

The portions, which are other than the first hydrogen collection portion73, of the cross-shaped convex portion 71 are guide portions 74 that areinclined downwardly in directions of moving away from the first hydrogencollection portion 73. Namely, the guide portions 74 which are inclineddownwardly toward outer edge portions of the top wall 70 are formed inall of the front side, the rear side, the right side and the left sideof the first hydrogen collection portion 73. The guide portions 74, dueto their sloping, guide the hydrogen whose specific gravity is low tothe first hydrogen collection portion 73.

Concretely, each of the guide portions 74 has a pair of side wallportions 74S that are connected to the adjacent general portions 72, anda ceiling wall portion 74T that connects the upper ends of the pair ofside wall portions 74S together. The pair of side wall portions 74Sextend in directions that are inclined slightly with respect to thevertical direction (refer to FIG. 4 and FIG. 5). Namely, when the guideportions 74 are cut along a plane orthogonal to the direction in whichthe guide portions 74 extend, cross-sectional shapes of the pairs ofside wall portions 74S substantially are truncated chevron shapes, and adistance between upper ends of the pair of side wall portions 74S isshorter than a distance between lower ends of the pair of side wallportions 74S.

A hydrogen sensing sensor 80, which senses the hydrogen that has beenaccumulated at the first hydrogen collection portion 73, is disposed atthe first hydrogen collection portion 73.

Further, a discharging mechanism 82 (see FIG. 3) is provided. Thedischarging mechanism 82 is a mechanism for discharging the hydrogenthat has been accumulated in the first hydrogen collection portion 73,and is structured to include a discharge hole 83, a shutter 84, and acontrol section 85. The discharge hole 83 is formed in the firsthydrogen collection portion 73, and the shutter 84 is structured so asto open and close the discharge hole 83. The control section 85 controlsthe opening and closing of the shutter in accordance with the output ofthe hydrogen sensing sensor 80.

Operation and Effects

The operation and effects of the present embodiment are described next.

In the present embodiment, the case 22 that has the bottom wall 44, theperipheral wall 46 and the top wall 70 is disposed beneath the floor ofthe vehicle cabin (at the vehicle lower side of the floor panel 16). Theplural high-pressure tanks 18 are accommodated within the case 22 so asto be lined up. Due thereto, in a high-pressure tank mounting structurein which the plural high-pressure tanks 18 are disposed beneath thefloor of a vehicle cabin, the high-pressure tanks 18 can be protectedfrom interference with the road surface and from fire.

Moreover, in the present embodiment, the first hydrogen collectionportion 73 that is recessed upwardly is formed at the back surface ofthe top wall 70 of the case 22. The hydrogen sensing sensor 80 isdisposed at the first hydrogen collection portion 73. Due thereto, thehydrogen that has permeated from the high-pressure tanks 18 can beaccumulated in the first hydrogen collection portion 73, and theaccumulated hydrogen can be sensed by the hydrogen sensing sensor 80.Accordingly, the hydrogen that stagnates within the case can be sensedeasily.

Further, in the present embodiment, the discharging mechanism 82, whichdischarges the hydrogen that has been accumulated at the first hydrogencollection portion 73, is provided. Due thereto, the hydrogen can bedischarged effectively.

Further, in the present embodiment, the discharging mechanism 82 isstructured to include the discharge hole 83, the shutter 84 and thecontrol section 85. The interior and exterior of the case 22 communicatevia the discharge hole 83. The discharge hole 83 is opened and closed bythe shutter 84. The control section 85 effects control so as to open andclose the shutter 84 in accordance with the output of the hydrogensensing sensor 80. Due thereto, for example, the shutter 84 is closed atusual times, and in case in which hydrogen is sensed, by opening theshutter 84, the hydrogen is discharged appropriately while penetrationof water and the like from the exterior can be suppressed.

Further, in the present embodiment, the first hydrogen collectionportion 73 is positioned at the vehicle longitudinal direction centralportion and the vehicle transverse direction central portion of the topwall 70. Due thereto, the hydrogen can be collected efficiently at thefirst hydrogen collection portion 73, as compared with a construction inwhich the first hydrogen collection portion 73 is positioned only in avicinity of the edge portion of the top wall 70 as seen in a vehicleplan view.

Further, in the present embodiment, the guide portions 74, which areinclined so as to slope downwardly toward the outer edge portions of thetop wall 70, are formed at all of the front side, the rear side, theright side and the left side of the first hydrogen collection portion73. Due thereto, as shown in FIG. 6, the hydrogen can be guided from theouter edge portions of the four directions by the guide portions 74 tothe first hydrogen collection portion 73, and can be discharged-outtherefrom.

Modified Example of Second Embodiment

Note that the above embodiment describes an example in which the guideportions 74, which are inclined so as to slope downwardly toward theouter edge portions of the top wall 70, are formed at all of the frontside, the rear side, the right side and the left side of the firsthydrogen collection portion 73. However, the guide portion 74 may beformed in at least one of the front side, the rear side, the right sideand the left side of the first hydrogen collection portion 73. Theportions where the guide portions 74 are not formed may be the generalportions 72.

Further, there may be a high-pressure tank unit 210 that relates tomodified example 1 and is shown in FIG. 7 and FIG. 8. In modifiedexample 1, in the same way as in the above-described embodiment, thefirst hydrogen collection portion 73 at which the hydrogen sensingsensor 80 is disposed is positioned at the vehicle longitudinaldirection central portion and the vehicle transverse direction centralportion of the top wall 70. On the other hand, the guide portions 74 areformed only at the front side and the rear side of the first hydrogencollection portion 73. Therefore, of the top wall 70, the both sideportions thereof that are at either side of the vehicle transversedirection central portion are the general portions 72. Further, as shownin FIG. 7, the convex portion 71 (the first hydrogen collection portion73 and the guide portions 74) overlaps with a tunnel portion 16T of thefloor panel 16, which structures the floor portion of the vehicle cabin,as seen in a vehicle plan view. Due thereto, the case 22 that has theconvex portion 71 can be mounted by utilizing the tunnel portion 16Tthat is convex upwardly at the floor panel 16, and therefore, it ispossible to place the high-pressure tank unit 210 at a relatively upperside of the vehicle. Note that, in modified example 1, the position ofthe first hydrogen collection portion 73 in the vehicle longitudinaldirection may be changed. For example, the first hydrogen collectionportion 73 may be positioned at the vehicle longitudinal direction frontend portion and the vehicle transverse direction central portion, or maybe positioned at the vehicle longitudinal direction rear end portion andthe vehicle transverse direction central portion.

Note that modified example 1 may be changed to a structure in which onlytwo of the guide portions are formed at the left side and the rightside. Due thereto, owing to the convex portion 71 that extends over theentire vehicle transverse direction, the hydrogen can be trapped by theguide portions 74 when the vehicle 11 tilts forward or tilts rearward,and can be sensed by the hydrogen sensing sensor 80 of the firsthydrogen collection portion 73.

Further, there may be a high-pressure tank unit 310 relating to modifiedexample 2 and shown in FIG. 9 and FIG. 10. In modified example 2, thefirst hydrogen collection portion 73 at which the hydrogen sensingsensor 80 is disposed is positioned at the vehicle longitudinaldirection rear end portion of the top wall 70. The first hydrogencollection portion 73 is formed over the entire vehicle transversedirection at the vehicle longitudinal direction rear end portion of thetop wall 70. The plural discharge holes 83 may be formed so as to belined up in the vehicle transverse direction at the first hydrogencollection portion 73. As shown in FIG. 9, the convex portion 71, whichis convex upwardly and is the portion of the top wall 70 where the firsthydrogen collection portion 73 is formed, is disposed so as to, as seenin a vehicle plan view, overlap a rear portion 16R that is formed in avicinity of a rear side of a rear seat at the floor panel 16. The rearportion 16R is convex toward the vehicle upper side with respect to thegeneral portions of the floor panel 16, and is inclined obliquely towardthe rear and upper side from the rear ends of the general portions, and,thereafter, extends toward the vehicle rear side in the horizontaldirection. Due thereto, the case 22 that has the first hydrogencollection portion 73 (the convex portion 71) can be mounted byutilizing the rear portion 16R that is convex upwardly at the floorpanel 16, and therefore, it is possible to place the high-pressure tankunit 310 at a relatively upper side of the vehicle.

Further, there may be a high-pressure tank unit 410 that relates tomodified example 3 and is shown in FIG. 11. Modified example 3 is astructure in which, in modified example 2, the guide portion 74, whichis inclined downwardly toward an outer edge portion (the front endportion) of the top wall 70, is formed at the front side of the firsthydrogen collection portion 73. The guide portion 74 is formed at thevehicle transverse direction central portion. Due thereto, the hydrogen,which has been trapped by the guide portion 74 that extends in thevehicle longitudinal direction, can be guided to the first hydrogencollection portion 73. Moreover, the first hydrogen collection portion73 is disposed so as to correspond to the rear portion 16R of the floorpanel 16, and the guide portion 74 is disposed so as to correspond tothe tunnel portion 16T of the floor panel 16. It is thereby possible toplace the high-pressure tank unit 410 at a relatively upper side of thevehicle.

Further, there may be the high-pressure tank unit 510 that relates tomodified example 4 and is shown in FIG. 12. Modified example 4 is astructure in which, in the above-described second embodiment (refer toFIG. 6 through FIG. 9), a second hydrogen collection portion 75, whichis recessed upwardly and is positioned further toward a vehicle lowerside than the first hydrogen collection portion 73, is formed at a backsurface of the outer peripheral portion of the top wall 70. Due thereto,the hydrogen is trapped once by the second hydrogen collection portion75, and is guided from the second hydrogen collection portion 75 via theguide portions 74 to the first hydrogen collection portion 73, and isdischarged-out therefrom. Because the outer peripheral portion of thetop wall 70 is a portion where the hydrogen is apt to be accumulated dueto tilting of the vehicle 11, discharging of the hydrogen can be carriedout effectively.

Note that, instead of the four guide portions 74 at the front, rear,left and right, modified example 4 may be changed to a structure inwhich only two of the guide portions at the front and the rear areformed, or may be changed to a structure in which only two of the guideportions at the left and right are formed.

Supplemental Description of Above Embodiments

Note that the above embodiments describe examples in which thedischarging mechanism 82, which is for discharging the hydrogen that hasbeen accumulated in the first hydrogen collection portion 73, isprovided. However, the present invention is not limited to this.

Further, the above embodiments describe examples in which thedischarging mechanism 82 is structured to include the discharge hole 83,the shutter 84 and the control section 85. However, the dischargingmechanism of the present invention is not limited to this. It sufficesfor the discharging mechanism to have at least the discharge hole thatcommunicates the interior and the exterior of the case.

Further, the above embodiments describe that the case main body 40 is abox whose upper side is open, and the opening at the upper side of thecase main body 40 is closed-off by the cover member 42 that is shaped asa flat plate. However, the case of the present invention is not limitedto this. For example, the case may be structured due to a box, whoselower side is open, being joined onto a bottom wall that is shaped as aflat plate.

What is claimed is:
 1. A high-pressure tank mounting structurecomprising: a case disposed beneath a floor of a vehicle cabin andhaving a bottom wall, a peripheral wall and a top wall; and a pluralityof high-pressure tanks accommodated so as to be lined up within thecase, wherein a first hydrogen collection portion that is recessedupwardly is formed at a back surface of the top wall of the case, andwherein a hydrogen sensing sensor is disposed at the first hydrogencollection portion.
 2. The high-pressure tank mounting structure ofclaim 1, further comprising a discharging mechanism discharging, to anexterior of the case, hydrogen that has been accumulated at the firsthydrogen collection portion.
 3. The high-pressure tank mountingstructure of claim 2, wherein the discharging mechanism comprises: adischarge hole (83) that communicates an interior of the case with theexterior of the case; a shutter that opens and closes the dischargehole; and a control section that controls opening and closing of theshutter in accordance with output of the hydrogen sensing sensor.
 4. Thehigh-pressure tank mounting structure of claim 1, wherein the firsthydrogen collection portion is positioned at a vehicle longitudinaldirection central portion and a vehicle transverse direction centralportion of the top wall.
 5. The high-pressure tank mounting structure ofclaim 1, wherein a guide portion, which is inclined downwardly toward anouter edge portion of the top wall, is formed at at least one of a frontside, a rear side, a right side and a left side of the first hydrogencollection portion.
 6. The high-pressure tank mounting structure ofclaim 1, wherein guide portions, which are inclined downwardly towardouter edge portions of the top wall, are formed at all of a front side,a rear side, a right side and a left side of the first hydrogencollection portion.
 7. The high-pressure tank mounting structure ofclaim 1, wherein: the first hydrogen collection portion is positioned ata vehicle transverse direction central portion of the top wall, a guideportion, which is inclined downwardly toward an outer edge portion ofthe top wall, is formed at a front side or a rear side of the firsthydrogen collection portion, and as seen in a vehicle plan view, thefirst hydrogen collection portion and the guide portion are configuredto overlap a tunnel portion of a floor panel that structures a floorportion of the vehicle cabin.
 8. The high-pressure tank mountingstructure of claim 5, wherein a second hydrogen collection portion,which is recessed upwardly and is positioned further toward a vehiclelower side than the first hydrogen collection portion, is formed at aback surface of an outer peripheral portion of the top wall.
 9. Thehigh-pressure tank mounting structure of claim 6, wherein a secondhydrogen collection portion, which is recessed upwardly and ispositioned further toward a vehicle lower side than the first hydrogencollection portion, is formed at a back surface of an outer peripheralportion of the top wall.
 10. The high-pressure tank mounting structureof claim 7, wherein a second hydrogen collection portion, which isrecessed upwardly and is positioned further toward a vehicle lower sidethan the first hydrogen collection portion, is formed at a back surfaceof an outer peripheral portion of the top wall.